<?php
var_dump($_GET);
var_dump($_POST);
var_dump($_REQUEST);
?>

<!DOCTYPE html>
<html>
    <head>
        <meta charset="utf-8">
        <title></title>
    </head>
    <body>
        <form method="post" action="全局变量POST.php?randnum=0.01">
            用户名：<input type="text" name="username" /><br />
            密码：<input type="password" name="password" /><br />
            <input type="submit" value="登录" />
        </form>
    </body>
</html>